Building power supplies as small and as efficient as possible is very important for many applications such as satellite power supplies and other space applications. At a launch cost of $25-50K per pound, the savings can be as much a s $10M per spacecraft if for example, 200 pounds of weight is saved. Several new generations of technology have progressively developed which have made power supplies smaller and more efficient. Power supply size can be reduce by two methods: 1) by using advanced packaging methods or 2) by using high frequency topologies or both.
One of the earlier forms of higher density power supply packaging technology used xe2x80x9csurface mountxe2x80x9d technology. With surface mount technology, discrete components such as integrated circuits, resistors, capacitors, inductors and transformers are individually qualified and tested and then installed in a printed circuit (PC) board. Most of the discrete components are surface mounted and when surfae mount components are not available or not reliable enough for the environments of space, some are connected by through holes where they are connected through the PC board.
An improvement in packing density was obtained by the use of multichip module (MCM) technology. Multi-chip module technology involves using bare integrated circuit (IC) dies which are interconnected through multi-layered MCM packaging technologies such as Hybrids. This provides closer spacing of components.
One earlier form of multichip module technology used for creating power supplies is referred to as hybrid technology. Hybrid packaging involves using bare IC dies placed in close proximity to discrete components such as transformers and multi-layer capacitors. These parts are mounted on multi-layered substrtates which form the interconnections. The whole power supply package is then hermetically sealed. This hybrid package provides a higher packing density than the convention surface mount technology.
The next generation of multi-chip module technology that provides even better packing density and heat conduction properties is referred to as xe2x80x9cHigh Density Interconnectxe2x80x9d (HDI) technology. HDI technology allows bare integrated dies to be mounted inside a ceramic block which conducts heat down into the bottom of the package while the chips are interconnected on the top of the package. Since the interconnects are performed on top of the components, the unused space required for routing in a traditional hybrid technology is eliminated and a 2:1 packing density improvement over hybrids can be achieved. Furthermore, since the active devices are in a substrate a good thermal path can be provided to a baseplate.
To further improve and maximize the density of power supplies, the switching frequency of the power supplies must be increased to lower the size and volume requirement of the passive components such as the magnetics or the capacitors. This method has already been implemented with switching frequencies up to 1-2 MHz. Above this frequency two limitations occur. One is the availability of high efficiency magnetic core material at these frequencies and the other is the interconnection of these components to the rest of the power supply circuit. At higher freqencies parasitic elements such as trace inductances become dominant and interfere with the desired operation of the power supply. What is needed is a packing technology that further improves upon HDI technology by providing even greater packing density to further reduce the parasitic elements while switching at 1-2 MHz range while increasing the power supply density without the need to go much higher in frequency. What is also needed is a packaging method that provides good heat conduction properties, power supply efficiency, is simple and inexpensive to build, and is effective for use in space applications.
The present invention is directed towards a multilayered circuit module and a method for constructing such a module, wherein the module has passive components such as capacitors, inductors, transformers distributed into a ceramic substrate. Since ferrite magnetics and mutilayer ceramics capacitors are the dominant volume drivers of a space power supply, this module provides an optimally close packing density of these components without wasting large areas of unused substrate. The module of the present invention weaves capacitors, inductors, and transformers into the substrate without the use of printed circuit boards and eliminating discrete components. The substrate of the module becomes a functional component itself, rather than just a block receptacle for discrete components. The module of the present invention provides a very densely packed power supply with good heat conduction properties and which is also less costly to build than HDI modules.